Planetary mill for producing scallop-free strip

ABSTRACT

This application discloses an improvement in planetary rolling mills, making possible a rolling of flat strip, free from scallop, without the need for a planishing mill to smooth out the scallops which are normally produced by a planetary mill. There is also disclosed how the angle of entry of the work rolls into the slab may be reduced, thus reducing the likelihood of surface defects, or alternatively, making it possible to roll thicker slabs than was possible heretofore on a given size planetary mill. The disclosure teaches that as a particular work roll enters the roll bite, its diametrically opposite work roll engages a cam. The cam has a surface corresponding generally to the circular orbit of the work roll, but is modified so as to deviate from such orbit by a very small amount. An initial deviation may cause the work roll diametrically opposite the rolls which are in engagement with the cam to engage the slab at a more acute angle to the passline, and a final deviation may cause the work rolls which are diametrically opposite rolls in contact with the cam, to follow a path parallel to the passline as they leave the roll bite.

United States Patent- "91 Sendzirnir 1 Feb. 5, 1974 PLANETARY MILL FORPRODUCING SCALLOP-FREE STRIP [76] Inventor: Tadeusz Sendzimir, PO. Box1350,

Waterbury, Conn. 06720 22 Filed: Oct. 5, 1972 21 Appl.No.:295,345

[52] US. Cl 72/190, 72/240, 72/241 Primary Examiner-Lowell A. Larson-Attorney, Agent, or Firm-Melville, Strasser, Foster & Hoffman 5 7ABSTRACT This application discloses an improvement in planetary rollingmills, making possible'a rolling of flat strip, free from scallop,without the need for a planishing mill to smooth out the scallops whichare normally produced by a planetary mill. There is also disclosed howthe angle of entry of the work rolls into the slab may be reduced, thusreducing the likelihood of surface defects, or alternatively, making itpossible to roll thicker slabs than was possible heretofore on a givensize planetary mill. The disclosure teaches that as a particular workroll enters the roll bite, its diametrically opposite work roll engagesa cam. The cam has a surface corresponding generally to the circularorbit of the work roll, but is modified so as to deviate from such orbitby a very small amount. An initial deviation may cause the work rolldiametrically opposite the rolls which are in engagement with the cam toengage the slab at a more acute angle to the passline, and a finaldeviation may cause the work rolls which are diametrically oppositerolls in contact with the cam, to follow a path parallel to the passlineas they leave the roll bite.

8 Claims, 4 Drawing Figures PATENTED FEB 51974 SHEEI 1 or 3 (PR/0k ART)FIG.

PATENTED EB 51974 SHEET 2 OF 3 PATENTEUFEB 519M 3.79.66

SHEEI 3 0F 3 f/G. Z

PLANETARY MILL FOR PRODUCING SCALLOP-FREE STRIP BRIEF SUMMARY OF THEINVENTION FIG. 1 is a longitudinal cross sectional view through Thepresent invention relates to an improvement in 5 a mill according to thepresent invention.

planetary mills such as are described in U. S. Pat. No. 2,710,550 whichmakes it possible to produce a scallop-free strip.

In a planetary mill, a heavy backing roll is surrounded by a pluralityof work rolls which orbit around the backing roll. The orbit of the workrolls is of course circular. The result of this situation is that thestrip produced is made up of short sections, each of which has beenrolled by one pair of the procession of work rolls. These shortsections, because of the circular orbit of the work rolls, show upnoticeably as small corrugations or scallops. In order to produce asaleable strip, it has been necessary to follow the conventionalplanetary mill with a so-called planishing mill. While the planishingmill has been successful in smoothing out the scallops produced by theplanetary mill, there are nevertheless drawbacks to such an arrangement.The stripin passing from the planetary mill to the planishing mill coolsat such a rate that it has to be substantially overheated in thefurnace, which results in increased scale losses and degradation of thesurface. It should be remembered that hot rolling must be completed onsuch materials as low carbon sheets for deep drawing, at temperaturesabove the AC3 recrystallization point (about 830 0.

I According to the present invention, the above mentioned difficultiesare overcome by causing the work rolls of the planetary mill to deviatevery slightly from their circular orbit during the last portion of theircontact with the workpiece, so that during this last portion of theircontact with the workpiece their path is parallel to the passline. Inthis way, the planetary mill will produce a finished strip and it ispossible to eliminate the conventional planishing mill. Furthermore,since the temperature of the workpiece increases by as much as 50 to 100C. in the roll bite,.the initial overheating of the slab can beeliminated with the consequent reduction in scale losses and improvementof the surface.

The present invention also contemplates a modification in the path ofthe workroll at its entry into the roll bite whereby the angle of entryis reduced or made more acute with respect to the pass line. If thereare slivers present in the slab, such defects tend to open up duringrolling on ordinary planetary mills and produce surface defects andrupture. However, with a more gradual entry into the roll bite, thesedangers are greatly reduced and slivers, if they are present, are morelikely to pass through the roll bite without defects opening up.Alternatively, it makes it possible for a given mill to roll a thickerslab than would otherwise be possible without exceeding the permissibleangle of entry of the rolls into the roll bite. It should be carefullynoted that these modifications of the roll path at the entry into, andexit from the roll bite, are in fact, and need be, very small. In nocase are they bigger than the natural elastic deflection of the backingroll of the planetary assembly rotating in its two chocks ahd having nosupplementary backing means as hereinafter described.

FIG. 2 is an elevational view with parts in section looking along thepassline of the structure shown in FIG. 1.

FIG. 3 is a cross sectional view on a greatly enlarged scale and brokenthrough the middle to conserve space showing at the bottom the path of awork roll and show-- ing at the top the path of a roll diametricallyopposite the particular work roll and in engagement with a cam.

FIG. 4 shows guide means according to the prior art, in a somewhatdiagrammatic manner.

DETAILED DESCRIPTION By referring to FIGS. 1 and 2 it will be observedthat the backing rolls 5 and 5 would be subject to deflection by theroll separating forces and would thus produce a strip which was thickerthan the roll gap had been set for, had they not been, in turn, bodiedby rigid beams. According to the invention, instead of backing beamsthere are provided the beam backed cams 8 and 8. From their locations,it will be observed that the cams 8 and 8 respectively are diametricallyopposite the roll bite of the mill so that pairs of diametricallyopposed work rolls are disposed with one in the roll bite and the otherbearing against the cam. The extent of the cams 8 and 8' around the workrolls is generally equivalent to the distance from when a work rollenters the roll bite to the point where it leaves the finished strip.

If the profile of the cams 8 and 8' are exactly circular so as to be inthe orbit of the work rolls when the mill is not loaded, i.e., whenthere is no roll separating force, roll deflection may be virtuallyeliminated be cause the beam and housing structure disclosed herein ismany times more rigid than the backing and work rolls.

However, applicant utilizes the above noted arrangement for controllingbacking roll deflection by means of the cams 8 and 8 to achieve majorimprovements in the design and operation of a planetary mill and in thequality of the finished product. Referring to FIG. 3,

' a work roll is shown at 6a as it first engages the slab at thebeginning of the roll bite. Its diametrically opposite work roll 6a isat the same time in contact with the cam 8. At 6b the work roll is shownas it leaves contact with the finished strip 1' while its diametricallyopposite work roll 6b is also in contact with the cam 8. It is these twopositions at the entrance into and at the exit from the roll bite whereuseful and important corrections are made by the means provided by thepresent invention. 'These improvements are distinct and apart from eachother. At the entrance of the work roll 6a into the roll bite, theobjective is to reduce the angle at which the orbit of the work roll 6aintersects the surface of the workpiece 1. For hot steel, an entranceangle of 16 is approximately the maximum which is permissible. Variousdefects result from too large an entrance angle and there-is a tendencyof slivers forming on the surface of the-workpiece if the angle ofincidence is greater than 169.

On the other hand, the part of the path of the work roll 6b where itmakes its last contact with the strip 1' should be flat, i.e., parallelto the passline in order to produce flat strip, so that the circularorbit of the work roll at 6b should be straightened out.

Both the above noted objectives are accomplished by the same means.Suitably shaped inflexible supports are provided for the work rollswhich are diametrically opposed to the work rolls which are in the rollbite and according to the present invention these inflexible supportsare in the form of beam-backed cams.

It must be observed that while the cam 8 will reduce or preventdeflection of the backing roll 5 under the influence of roll separatingforces, the cam can also be utilized to force the work roll 6 which isdiametrically opposite the work roll in contact with the cam, and thebacking roll 5 out of its non-loaded state in a direction to oppose theroll separating force and thereby roughly double the effect of thecorrection. It should be noted that deflection of the backing roll 5either by roll separating forces or by the effects of the cam causesstresses in the backing roll and excessive stresses will cause fatiguein the backing roll. Therefore the deviation produced by the cam must beless than an amount which would cause a deflection sufficient to producefatigue in the backing roll.

The entrance correction, i.e., the correction which causes the work rollentering the roll bite at 6a in FIG. 3 to enter at a more acute angle tothe passline, is produced by providing a projection 80 in the cam 8. Itwill be clear that as the work roll 6a moving clockwise in FIG.3 engagesthe projection 80, it will produce a downward deflection of the backingroll 5 which in turn will cause the work roll 6a entering the roll bitedown so that it enters the roll bite at a more acute angle x rather thanthe angle at which it would enter without such correction which isindicated at y. By the time the work roll 60 has reached a positionwhere the surface of the slab l is intersected by the unloaded orbit cof the work rolls and where therefore the roll separating force hasattained its full value, the profile of the cam 8 is hollowed outslightly in the opposite direction as indicated at 811. The result ofthis sequence of corrections at 8c and 8d as can be seen clearly fromFIG. 3, is that the angle of incidence is lowered from y to .r.

Since an entry angle of about 16 is permissible, it is obvious thatanother way of benefiting by applicants improvement is to increase thethickness of the slab 1 with the same mill and still maintain theentrance angle of 16. In this way a smaller planetary mill can take thesame slab which would normally require a much larger mill and of coursethis results in a great reduction in capital investment.

FIG. 3 also shows the configuration of the cam 8 which converts thepaths of the work rolls from circular to straight during the finalportion of the roll bite whereby to obtain a scallop-free strip. Thus,the portion of the cam 8 which is opposite the final portion of the rollbite is profiled to provide a protrustion 6e followed by a depression 6fand followed by a furtherprotrusion 6g approximately symmetrical to theprotrusion 6e. The total effect of these profile changes 6e, 6f, and 6gis to produce deflections of the backing roll 5 through the roll 6b andthereby to alter the path of the roll 6b as it is leaving the finishedstrip. The roll 6b is caused to follow a straight path from the point R(where it has been deflected by the protrusion 62) to the point Q (whereit is deflected by the protrusion6d).

It will be understood that the specific profiles described above are inthe nature of general rules and that the final shaping of the camprofile for a particular mill and for particular steels will take someexperimentation since each mill may behave slightly differently fromanother mill. Furthermore, roll flattening, unavoidable play inbearings, housing and beam deflections, small as they may be, stripthickness, and the like, have to be taken into consideration in order toproduce a truly smooth and even-gauged strip.

It is possible in some mills where the work rolls 6 are very small thattwo rolls may be in the roll bite simultaneously. In such a case theirdiameters must be such that the distance between them is considerablyshorter than the length of the roll bite, so that opposite rolls willnot enter the corrected profile sections of the cam 8 simultaneouslythereby interfering with one another.

Referring now back to FIGS. 1 and 2, the slab l is first reduced and fedforward by a pair of feed rolls 2 and 2 and thence through a pair ofguide rolls 3 and 3' and a further set of guide rolls 4 and 4 andfinally through the roll bite of the planetary assemblies 5 and 5' so asto emerge in the form of the strip 1,

The planetary assemblies 5 and 5' consist of backing rolls surrounded bywork rolls 6 and 6. The backing rolls run in bearings which are locatedin chocks 25 and 25 which chocks are slidably mounted against the wallof the housing 10 and adjustable by screwdown means such as the pressuremeans 27 (FIG. 1). The work rolls 6 and 6 are rotatably mounted inbearings located in cages 26 and 26' which are coaxial with the backingrolls and they are synchronized by means which are not shown. The rigidbeams 9 and 9' are connected to or preferably made integral with thehousing columns 10 and 10 to further reduce elastic deflection of thebeams 9 and 9. The cams 8 and 8 are installed in the beams 9 and 9 withwedges 11 and 11 interposed between the respective beams and cams. Bymeans of these wedges, the position of the cams in relation to thepassline may be adjusted by means such as the screws 28 and 28'.

It must be borne in mind that the portion of the slab 1 which is betweenthe bite of the rolls 2 and 2' and the planetary assemblies 5 and 5 issubject to strong and fluctuating upsetting forces produced byhorizontal components of roll pressure by the planetary rolls andopposed by the feed rolls through frictional contact with the slab 1 intheir roll bite. Since slabs are never perfectly straight or correct indimensions, guides have heretofore been provided which were parallel tobut clear of the top and bottom faces of the slab. In FIG. 4 such guides23 and 23 are shown diagrammatically to guide the end of the slab l andthe butting leading end of the next slab. Sheared ends of slabs arenever square and tend to slide off each other under the butting pressureif there were no guide to prevent it. However sliding contact with theslab produces scratches which are not removed by subsequent rolling.Consequently, the gap between the stationary guides on existing millsmust be wide enough to permit small deviations of the slab at the entryinto the planetary roll bite to avoid scratching. Such deviations cannotbe tolerated on mills, according to the present invention because thebenefits of the corrections of the roll paths would be substantiallydiminished.

Applicant obtains the necessary accuracy of slab position with respectto the passline and particularly at the entry into the planetary rollbite by providing contacting but non-sliding guides. In FIG. 1 there areshown guide rolls 4 and 4 which are fulcrumed on a common pin 14 whichis mounted in the column 10. The position of the rolls 4 and 4' iscontrolled by means of rods 15 and 15 which are positioned by wormdriven nuts 16 and 16' at their far end and engaging levers l7 and 17which carry the chocks for the rolls 4 and 4. In this way, theadjustment path of the rolls 4 and 4 is nearly parallel with the path ofthe planetary rolls so that the rolls 4 and 4' can be placed very closeto the roll bite entry. FIG. 1 also shows a pair of guide rolls 3 and 3'contacting the slab l ahead of the rolls 4 and 4'. While these rollscould be used to stabilize the slab jointly in the same way as the roll4 and 4, it is preferable to cause them to deflect the slab l slightlyso that the thrust to which the slab is subjected will press it againstone of the rolls 3 as shown. Once the slab is so deflected, it willcontinue to press against the roll 3' and the roll 3 may then bewithdrawn to the position indicated at 3 and shown in broken lines. Thismakes it possible to reduce the heat loss by the slab. The light flexingof the slab also insures a better correction of slab that may not havebeen straight originally.

With accurate guiding thus assured, and buckling prevented, the distancebetween the two roll bites is no longer critical. In other words, thefeed rolls do not have to be situated as close as possible to theplanetary rolls. FIG. 1 shows such a mill with the width of the column10 added to the minimum distance obtainable. This arrangement providesenough space for the installation of additional rapid heating means torestore a part of the heat loss suffered by the slab on its path fromthe furnace to the planetary roll bite. This is a very importantadvantage since the heat loss usually amounts to between 100 and 250 F.and imposes the need to overheat the slab in the furnace. This means alonger furnace together with fuel and scale losses. The rapid heatingmeans may be any of the well known means such as induced eddy currents,direct impinging, high temperature burners and the like. The heatingmeans shown in FIG. 1 (only between the feed rolls 2 and 2 and the guiderolls 3 and 3' so as not unnecessarily to complicate the figure) arehigh temperature resistors of refractory metals surrounded by quartztubes 18 and provided with water cooled reflector shields 19 which arepreferably made of a reflecting metal such as stainless steel. Theseprotect the slab 1 against radiation losses and also protect the millparts against heat damage. It may be also mentioned that for reasons ofdrawing clarity, butting guides have been omitted in FIG. 1.

It will be clearthat numerous modifications may be made withoutdeparting from the spirit of the invention. No limitations other thanthose specifically set forth in the claims are intended and no suchlimitations should be implied.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

-l. A planetary mill for rolling flat articles, comprising a millhousing, at least one backing roll mounted in said housing, and having anumber of planetary work rolls orbiting around it, and a cam arranged tocontact the major part of the face of the work roll which isdiametrically opposite the work roll which is actually in the roll bite,said cam being mounted in a rigid beam secured to said mil] housing,said cam having a surface generally following the circular orbit of thework rolls, but modified gradually out of said orbit by a radialdistance less than the deflection which would cause fatigue stresses insaid backing roll.

2. A mill according to claim 1 wherein said cam is modified in its lastportion, which corresponds to the last portion of the roll bite of thediametrically opposite work roll, to cause said last named work rollduring said last portion of the roll bite, to follow a straight lineparallel to the passline.

3. A mill according to claim I, wherein said cam is modified in itsinitial portion, which corresponds to the first contact of thediametrically opposite work roll with the workpiece, and up to the pointwhere the roll separating force has reached its full value, to causesaid last named work roll to follow a path at a more acute angle to thepassline than it would follow without said modification. I

4. A mill according to claim 1, wherein two work rolls are in the rollbite simultaneously during at least a part of the cycle, and whereinsaid cam is modified for two diametrically opposite work rolls insuccession, and wherein the distance between succeeding work rolls issubstantially less than the length of the roll bite, to avoidinterference of the two profile modifications of the cam surface.

5. A mill according to claim 1, wherein non-slidable slab guiding meansare provided, said means contacting at least a part of the face of theslab, said guiding means being disposed close to the roll bite entry toinsure the exact position of the slab with respect to the passline.

6. A mill according to claim 5, wherein said guiding means comprisesmall diameter rolls.

7. A mill according to claim 6, wherein additional opposed guide rollsare disposed ahead of said small diameter rolls, at least one of saidadditional guide rolls being positioned to deflect the slab slightlyinto a curve, whereby to produce a pressure component forcing one faceof said slab against the opposite guide roll.

8. A mill according to claim 7, wherein the distance between saidadditional opposed guide rolls is less than the length in which the slabwould buckle.

1. A planetary mill for rolling flat articles, comprising a millhousing, at least one backing roll mounted in said housing, and having anumber of planetary work rolls orbiting around it, and a cam arranged tocontact the major part of the face of the work roll which isdiametrically opposite the work roll which is actually in the roll bite,said cam being mounted in a rigid beam secured to said mill housing,said cam having a surface generally following the circular orbit of thework rolls, but modified gradually out of said orbit by a radialdistance less than the deflection which would cause fatigue stresses insaid backing roll.
 2. A mill according to claim 1 wherein said cam ismodified in its last portion, which corresponds to the last portion ofthe roll bite of the diametrically opposite work roll, to cause saidlast named work roll during said last portion of the roll bite, tofollow a straight line parallel to the passline.
 3. A mill according toclaim 1, wherein said cam is modified in its initial portion, whichcorresponds to the first contact of the diaMetrically opposite work rollwith the workpiece, and up to the point where the roll separating forcehas reached its full value, to cause said last named work roll to followa path at a more acute angle to the passline than it would followwithout said modification.
 4. A mill according to claim 1, wherein twowork rolls are in the roll bite simultaneously during at least a part ofthe cycle, and wherein said cam is modified for two diametricallyopposite work rolls in succession, and wherein the distance betweensucceeding work rolls is substantially less than the length of the rollbite, to avoid interference of the two profile modifications of the camsurface.
 5. A mill according to claim 1, wherein non-slidable slabguiding means are provided, said means contacting at least a part of theface of the slab, said guiding means being disposed close to the rollbite entry to insure the exact position of the slab with respect to thepassline.
 6. A mill according to claim 5, wherein said guiding meanscomprise small diameter rolls.
 7. A mill according to claim 6, whereinadditional opposed guide rolls are disposed ahead of said small diameterrolls, at least one of said additional guide rolls being positioned todeflect the slab slightly into a curve, whereby to produce a pressurecomponent forcing one face of said slab against the opposite guide roll.8. A mill according to claim 7, wherein the distance between saidadditional opposed guide rolls is less than the length in which the slabwould buckle.